Human Scent Is Even Sweeter For Malaria Mosquitoes

Mosquitoes detect odors with their antennae. Here an Anopheles gambaie mosquito has been beheaded to photograph its antennae and eyes.

Courtesy of the Zwiebel Lab/Vanderbilt University

Originally published on May 16, 2013 1:13 pm

People smell yummy to mosquitoes.

So yummy, in fact, that our scent is a big way the pesky insects track us down.

But just how much mosquitoes like Eau de Human may not be entirely up to the bugs.

Mosquitoes are more attracted to human odors when they're infected with the malaria parasite, scientists reported Wednesday in the journal PLOS ONE.

Entomologists at the London School of Hygiene and Tropical Medicine gave malaria-transmitting mosquitoes two places to land: a clean, nylon stocking and one worn for 20 hours on the foot of young Dutch woman (who happens to be an author on the study).

All the mosquitoes gravitated more toward the dirty sock than the fresh one. But the bugs infected with malaria landed on the smelly nylon more frequently. And while they were there, the parasite-possessed bugs were more likely to try and bite the stocking than the malaria-free insects.

It's almost like mind control. The parasite changes the behavior of the insects for its own benefit. The more biting the bugs do, the more they spread the protists.

This kind of parasitic mind control isn't limited to mosquitoes and malaria. One type of fungus is notorious for turning carpenter ants into so-called zombies. After the Ophiocordyceps unilateralis infects the ants, the insects march to a precise location on a leaf that is optimal for dispersing the fungus's spores. Eventually, the ant dies at this location and the Ophiocordyceps sprouts from the dead corpse.

Malaria appears to be more subtle with its subterfuge. It just amplifies the mosquitoes' preference for human blood.

Scientists have known for a decades that the malaria vector Anopheles gambaie is highly attracted to people. In fact, these ladies – it's only the females that bite us — actually prefer to feast on humans than many other animals. They even have a strong aversion to cow odor.

So what's in our bouquet that makes us so alluring to mosquitoes?

Human skin emits over 350 different odor molecules. The An. gambaie mosquitoes have odor receptors in their antennae specifically built to detect a handful of these scents.

One these compounds, known as mushroom alcohol (because it's made by mushrooms), gives our skin a moldy or meaty smell. Another compound, diacetyl, has a buttery scent. It's the same molecule found in Chardonnay and added to microwave popcorn to simulate butter.